Process for the production of molybdenum and tungsten and their alloys using amalgams



United States Patent Ofi ice 3,480,428 Patented Nov. 25, 1969 3,480,428 PROCESS FOR THE PRODUCTION OF MOLYBDE- NUM AND TUNGSTEN AND THEIR ALLOYS USING AMALGAMS Gerhard Jangg, Gebreidemarkt 9, Vienna A1060, Austria No Drawing. Filed Feb. 7, 1967, Ser. No. 614,416 Int. Cl. C22d 1/24, 1/26, 5/00 US. Cl. 7584.5 9 Claims ABSTRACT OF THE DISCLOSURE Process for preparing molybdenum and tungsten by reacting a halide of molybdenum or tungsten with a quantity of zinc amalgam. The quantity of zinc amalgam employed is in excess of the stoichiometric amount needed to reduce the halide to the metallic state. The reaction mixture essentially consisting of zinc halide, an amalgam of molybdenum or tungsten, and excess of metallic zinc, is heated to a temperature at least close to or above the melting temperature of the zinc halide. The reaction mixture is then cooled to solidify it and to separate the zinc halide from the amalgam. The mercury and the excess zincare then separated from molybdenum or tungsten by distilling.

SUMMARY OF THE INVENTIDN The present invention relates to a process for the production of molybdenum or tungsten and their alloys by an amalgam-metallurgical method.

' The advantages of using mercury as an assistant metal in the production of non-precious metals, which is usually achieved by the reduction of their halides with alkaline or alkaline earth metals, has been the subject of several prior proposals in the patent literature.

The advantages consist mainly in the fact that the reaction with the reduction metals as diluted by the mercury, can be easily regulatedand carried out continually while the amalgams do not absorb non-metallic impurities or can be easily freed from them, so that after removing the mercury by distilaltion, very pure products can be obtained that are essentially free from any metalloids.

Processes using amalgams of the alkaline and alkaline earth metals instead of the elementary metals for the reduction of compounds of non-precious metals, preferably their halides have been hitherto proposed for the production of uranium, thorium, titanium, zirconium, hafnium, niobium and tantalum. While the reaction of the halides of said metals with the amalgams gives no difiiculties the further processing of the reaction mixtures is very difiicult. For uranium and thorium this is achieved by treating the mixture with diluted, non-oxidizing acids, which are free from air. For titanium, zirconium, hafnium, niobium and tantalum, acids containing complex forming materials or readily complex forming hydrofluoric acid have to be used.

Processes at which the processing is done by dry methods, viz distillation, of all -by-products from the required or remaining metal or melting of the reaction products at high temperatures, entails specialised high pressure apparatus owing to the high vapor pressure of the mercury which arises on separation of the amalgam and saline byproducts, which apparatus is not suitable for commercial use or technology.

Our investigations have shown, that halides of molybdenum and tunsten can, in contrast to the halides of the other non-precious metals (viz uranium, thorium, titanium, zirconium, hafnium, niobium and tantalum) be reduced to the metallic state by zinc amalgam.

It is therefore an object of this invention to provide a process for the simple and economic production of molybdenum or tungsten metal which comprises reducing a halide, preferably a chloride of molybdenum or tungsten with a quantity of zinc amalgam in excess of that theoretically necessary for complete reduction, heating the reaction mixture to a temperature close to or higher than the melting point of the resulting zinc halides or chloride, cooling and separating the solidified zinc halides or chloride from the amalgam and distilling the mercury and excess zinc from the required residual metallic molybdenum or tungsten.

The reaction forms an intense mixture of the amalgams of said metals, which mixture contains an excess of the reduction metal zinc, and the resulting by-product e.g. zinc-chloride. The low melting point of the zinc-chloride (318 C.) enables a simple processing of the reaction mixture by melting under normal pressure. At temperatures higher than 310 C. the molten zinc-chloride separates completely from the amalgam.

After cooling, the zinc-chloride solidifies, forming a solid cake, which can be lifted off without difliculty from the amalgam, which latter still contains some metallic zinc. The mercury and the metallic zinc are then distilled from the pure and dried amalgam, the required metal remaining as a residue in the form of a fine powder or as a sponge-like mass, according to the maximum temperature reached during the distillation.

h temperatures higher than the melting point of the zincchloride the reaction rate falls off slightly. It is therefore advantageous to work at temperatures closely below the melting point of the zinc-chloride, although it is also possi- -ble to get high reaction rates and high yields at other temperatures. By mixing the amalgams of molybdenum or tungsten, obtained by the method herein described with amalgams of other metals, obtained by other known methods for example by reduction of their halides with an alkali-almalgam or by electrodeposition of the metals at mercury cathodes and then effecting distillation of the mercury and zinc from the mixed amalgams, alloys of molybdenum or tungsten with these other metals can be obtained. These alloys are obtained in the form of fine powders or as a sponge-like mass according to the maximum temperature reached during distillation.

Powders obtained from these mixed amalgams are absolutely homogeneous even at low working temperatures and in contrast to similar powders obtained by sintering the components. In carrying out the process according to this invention of producing molybdenum or tungsten, zinc chloride or other zinc halide is obtained as a by-product, which without difiiculty can be used for the production of zinc amalgam, as used as the reduction agent.

Fused zinc chloride, formed in the herein described process for production of molybdenum or tungsten, can be dissolved in water and the resulting solution can be electrolysed on a mercury cathode in a well known manner, the deposited zinc thus forming zinc-amalgam.

The following examples illustrate the method embodying the present invention:

EXAMPLE 1 g. molybdenum chloride, according to the formula M001 are allowed to react with 1800 g. zinc-amalgam, containing 4% by weight of zinc, by intensive mixing during 4 hours at a temperature of 200 C. Without mixing or agitation the reaction products are then heated to 350 C. for 30 minutes and finally cooled. Zinc chloride is then separated mechanically and the mercury and the remaining zinc distilled from the amalgam in vacuum, the temperture during the distillation being finally raised to 800 C. As a residue 30 g. of molybdenum-metal powder, free from zinc and mercury is obtained.

EXAMPLE 2 100 g. tungsten-chloride, of the formula WCl and 3000 g. zinc-amalgam containing 2% by weight of zinc are heated for 4 hours to 250 C. and mixed vigorously all the time. Then the reaction mixture is heated to 350 C. for 30 minutes without agitation, thus allowing the mixture to separate.

After cooling solidified zinc-chloride is removed and mercury and zinc are distilled from the amalgam. There then remains 45 g. of finely powdered tungsten metal free from zinc and mercury.

What I claim is:

1. Process of producing molybdenum or tungsten, comprising the steps of reacting a chloride of molybdenum or tungsten with a quantity of zinc amalgam in excess of the stoichiometric amount required to reduce the chloride to the metallic state, whereby a reaction mixture of an amalgam of molybdenum or tungsten, zinc chloride and excess zinc is formed, heating the reaction mixture to a temperature at least close to the melting point of the zinc chloride, cooling the reaction mixture to solidify zinc chloride, separating the solidified zinc chloride from the amalgam, and distilling mercury and excess zinc from the amalgam to obtain metallic molybdenum or tungsten.

2. A process as set forth in claim 1, wherein the zinc amalgam is used in the range of 110 to 200 percent of the stoichicmetric amount required to achieve complete reduction.

3. A process as set forth in claim 1, wherein the zinc amalgam is used in the range of 120 to 150 percent of the stoichiometric amount required to achieve complete reduction.

4. A process as set forth in claim 1, wherein the amount of zinc in the zinc amalgam is in the range of 1 to percent by weight.

5. A process as set forth in claim 1', wherein the amount of zinc in the zinc amalgam is in the range of 2 to 5 percent by Weight.

6. A process as claimed in claim 1, wherein the reaction is carried out in the temperature range of about 20 to 400 C.

7. A process as claimed in claim 1, wherein the reaction is carried out in the temperature range of about 20 to 400 C.

8. A process as set forth in claim 1, comprising the additional step of mixing the molybdenum or tungsten amalgam obtained from the reaction, with an alkali amalgam and distilling mercury and zinc from the mixed amalgams.

9. A process as set forth in claim 1, comprising the step of dissolving the zinc chloride formed in the reaction in water, electrolyzing the mixture of zinc chloride and water utilizing a mercury cathode for depositing the zinc on the mercury cathode, whereby the deposited zinc forms zinc amalgam.

References Cited UNITED STATES PATENTS 2,371,829 3/1945 Kuss et al 204124 X 2,618,549 11/1952 Glasser et al. 84.5 2,618,550 11/1952 Hampel et a1. 7584.5 2,703,752 3/1955 Glasser et al. 7584.5X 2,813,787 11/1957 Schmidt 7584.5

FOREIGN PATENTS 542,182 6/1957 Canada. 932,168 7 1963 Great Britain.

OTHER REFERENCES Sidgwick, N. V., The Chemical Elements and Their Compounds, vol. II, Oxford University Press, London, 1950, pp. 1067-68.

L. DEWAYNE RUTLEDGE, Primary Examiner G. K. WHITE, Assistant Examiner US Cl. X.R. 20494, 124 

